Factors Influencing the Use of Tobacco Among Youth in Low-Income, Lower-Middle-Income, and Upper-Middle-Income Countries: A Systematic Review

Background: The use of tobacco is a significant global public health issue. According to the World Health Organization, tobacco use is a considerable risk factor for many diseases and causes more than 8 million deaths per year, with a disproportionate impact on low- and middle-income countries. Therefore, this systematic review was conducted to identify the factors influencing tobacco use among youth in low-income, lower-middle-income, and upper-middle-income countries. Study Design: A system review. Methods: The review followed the PRISMA guidelines, and the protocol was registered on PROSPERO (CRD42023430552). Several data sources were utilized, including PubMed, Scopus, ScienceDirect, MEDLINE, CINAHL, and ProQuest, and cross-sectional data from participants aged 15‒24 underwent investigation. Original full-text articles have been published between 2015 and 2023. Out of the 2892 studies, 20 were included in this review after two reviewers confirmed the eligibility criteria. Results: The average age of the participants was (mean±standard deviation: 19.45±1.686). Most studies were conducted in lower-middle and upper-middle-income countries. Frequently reported influences were at the individual and social levels, including demographic, economic, and psychological parameters, attitude and knowledge, individual behavioral factors, parental education, family member tobacco use, stressful life events, and social networks. At the environmental level, factors included secondhand smoke exposure, community context, media channels, and access to tobacco. Conclusion: The findings demonstrated a significant association between youth tobacco use and individual-, social-, and environmental-level factors. Consequently, specific interventions targeting these factors should be deployed to mitigate youth tobacco use in various socioeconomic settings.

mental health issues, and respiratory diseases. 6The burden of morbidity and mortality from these diseases is strongly linked with tobacco use in low-income, lower-middleincome, and upper-middle-income countries. 8Moreover, tobacco consumption impacts the spread of poverty and inequality by diverting household resources away from essential needs, subsequently reducing productivity and income, and increasing healthcare expenditures. 9urther, tobacco use has harmful environmental impacts that adversely affect the livelihood and well-being of individuals in low-and middle-income countries. 10he World Bank ranks world economies into four group classes of income in July each year based on gross national income per capita. 11,12The present group classification identifies 26 countries as low-income and 108 as middleincome, further divided into 60 upper-middle-income and 48 lower-middle-income countries. 11Overall, these countries account for approximately 75% of the global population and contribute to 40% of the world's economic activity. 12These outcomes emphasize the necessity of coordinated attempts to reduce tobacco consumption among youth in low-income, lower-middle-income, and middle-income countries.
The youth populations are specifically prone to engaging in tobacco use due to the influence of numerous factors such as peer pressure, social norms, and targeted marketing schemes used by the tobacco industry. 13The early initiation of tobacco use has profound effects on both physical and cognitive development. 14Individuals who initiate tobacco smoking at an early age are more prone to developing tobacco addiction and face greater challenges when struggling to quit smoking in adulthood. 15A further systematic review suggested that most studies were conducted in high-income countries, despite youth smoking rates being substantially higher in lower-and middle-income countries. 16Moreover, understanding the socioeconomic determinants of youth tobacco smoking is crucial for effective interventions. 17Therefore, it is necessary to conduct research on factors affecting tobacco use within diverse socioeconomic contexts to develop tailored interventions and address the consequences of tobacco-related diseases and disparities.Significantly, based on the current body of knowledge, this systematic review represents the first comprehensive examination of factors associated with tobacco use among youth in lowincome, lower-middle-income, and upper-middle-income countries.
The primary objective of this systematic review was to investigate factors influencing tobacco use among youth in low-income, lower-middle-income, and upper-middleincome countries.

Study design
This systematic review followed the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). 18The review adhered to the 27-item checklist and revised the flowchart provided in the PRISMA guidelines.The protocol for this systematic review was registered in PROSPERO (CRD42023430552).

Population, exposure, comparison, outcome, and study design criteria
Population: It included individuals who fall within the age range of 15-24, as defined by the United Nations youth definition, 19,20 and who have used any form of tobacco (i.e., cigarettes, cigars, smokeless tobacco, hookah, heated tobacco products, nicotine pouches, or e-cigarettes) within the last 30 days.Additionally, these individuals reside in countries that fall under the classification of lowincome, lower-middle-income, or upper-middle-income, as determined by the World Bank. 12xposure: Influencing factors.

Selection criteria
The study was based on original research and available full texts.[23]

Search strategy
Multiple databases, such as PubMed, Scopus, ScienceDirect, MEDLINE, CINAHL, and ProQuest, were extensively searched using generated MeSH (Medical Subject Headings) terms and keywords.They included factors influencing OR predictors influencing OR identifying factors OR associated factors AND tobacco abuse OR cigarette consumption OR chewing tobacco OR smokeless tobacco, AND youth OR young people OR adolescents.After searching, the studies were selected in accordance with the 2022 World Bank Index of Economic Classifications, 12 which encompasses countries with low-income, lower-middle-income, and upper-middleincome status.Moreover, the investigators formulated and implemented search methodologies under the guidance of a skilled health science librarian.

Study selection
The initial search across databases yielded 2892 articles (Figure 1).Two independent reviewers screened the titles and abstracts of potential articles to determine the eligibility criteria.If an article potentially met the inclusion criteria, the complete article was obtained and reviewed to confirm eligibility and inclusion in the review.Disagreements between reviewers were resolved through discussion or the involvement of a third reviewer when necessary.
Nine hundred duplicate articles were removed using the EndNote 21 "find duplicate" library feature and manual inspection.During the title and abstract screening Factors influencing the use of tobacco among youth process, 1873 records were excluded based on failure to meet study eligibility criteria.Of these, 500 articles did not address factors associated with youth tobacco use, and the remaining 1373 articles were not specific to the study objective.In addition, one article did not retrieve the full text. 24Next, full-text versions were obtained for the remaining 118 articles.Two authors (F. A. M. and S. R.) independently reviewed these articles based on the inclusion and exclusion criteria.After the full-text review, 20 articles were determined to be eligible and included in this systematic review.

Data extraction
The data extracted from these studies were synthesized and summarized using the matrix method 25 and the narrative synthesis technique. 26

Quality appraisal assessment
The authors systematically assessed the methodological quality of all 20 eligible studies using the Joanna Briggs Institute Meta-Analysis Assessment and Review Instrument. 48Critical appraisal tools for cross-sectional studies were used to evaluate the methodological quality of eligible studies.This tool covers eight components, including the study objectives, inclusion criteria, information about study participants and setting, measurement quality, identification and management of potential confounding variables, and statistical analyses.First, the eight components were rated on a three-point scale (1 = strong, 2 = moderate, or 3 = weak) based on the defined quality rating criteria. 49An overall "strong" rating was defined as having no weak and at least six strong ratings.An overall "moderate" rating was described as one weak and less than six strong ratings.A "weak" rating

Results
Out of the 2,892 articles identified, 20 met the study eligibility criteria.Studies included in the review used a cross-sectional design.The average age (M ± standard deviation) was 19.45 ± 1.686.The sample size ranged from 290 to 13,329 (M = 2,054).The majority of studies were conducted in lower-middle-income countries (n = 11), followed by upper-middle-income countries (n = 7) and low-income countries (n = 2) According to the quality appraisal evaluation (Figure 2), out of the eligible studies, fourteen 28,30-35,37-39, 41, 42, 45, 47 were rated as strong, while five 29,36,40,43,44 were rated as moderate in methodological rigor.Therefore, many studies had sound research designs and methodologies, which can lead to dependable and valid outcomes.However, one study 46 received a weak rating, revealing areas where their methodologies could be enhanced to boost their overall quality and dependability.

The main findings reported on the theory of triadic influence
Across all included studies, the most reported influences were on individual-(n = 18) and social-(n = 13) level factors, and fewer studies measured environmental-level factors (n = 10).The main findings are outlined in Table 2 and discussed later, according to the country's level.

Factors influencing tobacco use in upper-middle-income countries
Individual-level factors: This included demographics, economic status, psychological parameters, attitudes, and knowledge, as well as individual behavioral factors; four studies [28][29][30][31] revealed that males are more prone to tobacco use than females.One study 32 demonstrated that the high availability of money was also a significant factor in tobacco use.The findings of another study 33 showed severe depressive symptoms, and one study 29 showed that favorable or equivocal attitudes were positively associated with tobacco use.Three studies 28,30,33 found that alcohol consumption and other illicit drugs increased the likelihood of tobacco use among youth.
Social-level factors: They consisted of parents' education, peers' tobacco use, and stressful life events.One study 29 revealed that mothers with primary-level education increased the likelihood of tobacco use among youth.Another study 31 indicated that the use of electronic cigarettes by peers increased the likelihood of tobacco use among youth.Further, one 34 showed poor academic performance, and another 34 indicated that family circumstances, such as divorced parents and the death of one or both parents, increased the likelihood of tobacco use.
Environmental factors: Three studies 30,32,33 reported that secondhand smoke exposure is linked to higher rates of tobacco use among youth across various settings such as homes, restaurants, schools, public transport, or living with smokers.

Factors influencing tobacco use in lower-middle-income countries
Individual factors.Various demographic, economic, psychological, attitude and knowledge, and individual behavioral factors were found to be positively correlated with tobacco use among youth.These factors were included in six studies [35][36][37][38][39][40] on gender (male), three studies [40][41][42] on low education level, and three studies 40,43,44 that have shown that unmarried individuals and those living away from their families may have fewer social constraints and are more likely to engage in tobacco.One study 45 revealed low monthly income, and two studies 36,40 showed that high financial status significantly increased the likelihood of tobacco use.One study 38 demonstrated poor knowledge and neutral attitudes about smoking harm.Further, another study 44 reported relaxation and coping with stress.Moreover, two studies 38,44 showed that they intended to use tobacco and alcohol.
Social-level factors: They included family members smoking, stressful life events, and social networking.One study 45 indicated that father and brother's tobacco smoking was associated with tobacco use among youths.Further, another study 41 indicated that family conflict and poor family support also increase the likelihood of tobacco smoking.Four studies 36,39,41,45 represented that peer tobacco smoking and other illicit drug use were associated with tobacco use among youth.Additionally, three studies demonstrated that interaction with antisocial peers, 41 living with friends, 35 and social gatherings 44 among youth had a positive association with tobacco use.
Environmental-level factors: They encompassed media channels, community context, and access to tobacco.Two studies revealed that exposure to tobacco smoking by radio 42 and smoking advertising 37 increases tobacco use.In contrast, one study 44 reported that a lack of antismoking information on social media and traditional media is associated with its use among youth.Moreover, other studies showed that exposure to smoking in school locations 41 and living in rural areas 40,43 increased the likelihood of tobacco consumption among youth.Furthermore, three studies 37,39,41 found that the easy availability of tobacco in markets and communities increased the likelihood of tobacco use among youth.

Factors influencing tobacco use in low-income countries
Individual-level factors: They consisted of psychological and behavioral parameters.One study 47 indicated that curiosity and enjoyment were significantly associated with tobacco smoking among youth.Additionally, a study 46 confirmed that the use of illegal drugs and alcohol consumption increased the likelihood of tobacco smoking among youths.
Social-level factors: They included social networks and stressful life events.Two studies 46,47 reported that tobacco-smoking friends played an important role in tobacco use among youth.One study 47 revealed that life stress was significantly associated with tobacco smoking among youth.

Discussion
This systematic review explored factors influencing tobacco use among youth in low-, lower-, and uppermiddle-income countries.The review included 20 studies after narrowing down potentially relevant studies for the full text and considering the inclusion criteria.All included studies used cross-sectional designs that met the eligibility criteria for the review.The overall study quality varied from weak to strong.The primary factors that compromised methodological rigor were approaches utilized to address the confounding factors.Addressing potential confounding factors can be achieved using restriction, matching, and statistical adjustment methods. 50For instance, when investigating the correlation between factors influencing youth tobacco use, validity can be improved by limiting the study population, matching participants with similar characteristics, and employing statistical techniques such as regression to manage confounding variables. 48There was variation in the prevalence of tobacco use among different income categories of countries, with higher rates observed in lower-middle-income countries.
Studies included in the review investigated factors associated with three identified domains, namely, individual-, social-, and environmental-level factors.One individual-level factor was demographics.[31][35][36][37][38][39][40] According to the global gender gap report 2022, 51 men globally show a lower healthy life expectancy than women, apart from Sub-Saharan Africa.Furthermore, men are at a higher risk of mortality due to non-communicable diseases, such as cardiovascular diseases, cancers, respiratory diseases, and diabetes, than women.Therefore, it is suggested that health policies and programs that consider the unique needs and preferences of both men and women be promoted and implemented in the future.

Socioeconomic status
There was an inconsistent relationship between financial status and tobacco use among youth in lower-middleincome countries.In two studies, 36,40 higher income or daily pocket money was associated with increased tobacco use, whereas one study 45 found that lower income was also significant.This may reflect the various levels of affordability and accessibility of tobacco products in different settings and the different motivations and influences of tobacco use among youth.

Psychological and behavioral factors
Studies 29,41,47 conducted in low-income, lower-income, and upper-middle-income countries proved a positive association between favorable attitude, intention, and curiosity toward tobacco use.Earlier systematic reviews and meta-analyses revealed a positive association between favorable attitudes, intentions, and curiosity toward tobacco use among adolescents. 52Furthermore, studies 44,47 from low-and lower-middle-income countries demonstrated that stress coping levels and relaxation had a significant relationship with tobacco use among youth.These findings underscore the importance of implementing comprehensive programs focusing on tobacco prevention and providing youth with effective stress-coping mechanisms and relaxation skills.In addition, regarding substance use, one study from lowincome countries and another from upper-middle-income countries confirmed a positive association between tobacco use and individuals who were already consuming alcohol and using other illicit drugs. 28,47In an earlier review of a multi-country analysis, tobacco use was found to be influenced by alcohol consumption and other illicit drug use. 53This study indicated an explicit relationship between tobacco consumption, alcohol consumption, and other illicit drug use in low-and middle-income countries.

Social factors
Family impacts are essential components of the tobacco use behavior of youth. 54This study explicitly identified a significant relationship between tobacco use and factors influencing father and brother's tobacco use and family conflicts in lower-middle-income countries. 45n comparison, a previous systematic review consistent with 41 studies in 20 low-and middle-income countries represented compelling evidence of an association between parental and sibling tobacco smoking and tobacco use among youths.Furthermore, the study also indicated that family conflicts, low parental monitoring, and poor parent-child communication are factors that affect youth tobacco use. 55Moreover, one study in an upper-middleincome country found that the lower education of mothers significantly increased the likelihood of tobacco use among youth. 29A previous review of education and tobacco use suggested that education may reduce tobacco consumption. 55Peer influence on tobacco use and other types of illicit drug use among youth was significant in two low-income countries 46,47 and four lower-middleincome countries. 36,39,41,45Similarly, one study showed that peer tobacco use has a positive relationship with youth tobacco use. 53

Environmental factors
Two studies 42,44 conducted in lower-middle-income countries revealed that not using social media and traditional media, such as newspapers or television, and a lack of awareness about the harms of tobacco were positively associated with tobacco use.In contrast, an earlier survey performed among adolescents in 10 lowincome countries in Africa and Asia has proven a positive correlation between tobacco use and exposure to tobacco advertising and promotion across multiple mass media platforms.Another study showed a negative correlation between tobacco use and awareness of the detrimental effects of tobacco use, as well as exposure to mass media anti-tobacco messages. 56t is essential to acknowledge the limitations of this systematic review when interpreting the findings.The major limitation of this study is the need for more generalizability on the youth of high-income countries because the studies consisted of only low-income, lowerincome, and upper-middle-income countries.In addition, publication bias may occur due to the study period being limited between 2015 and 2023, which excludes studies published before this time limit.Furthermore, studies were excluded based on the definition of youth age.However, it is essential to consider the limitations of the studies with moderate and weak ratings, as they may have flaws in their methods or analyses.
This systematic review suggests that tobacco education programs should focus on mothers' education levels.Further, it is important to address individual-, social-, and environmental-level factors such as male gender and psychological issues, as well as the influence of social networks, including peers, across various settings.Tailored interventions such as peer support, social norm change, and awareness campaigns that adhere to strict marketing regulations through social and traditional media should be explored for their effectiveness.

Conclusion
The findings are categorized into individual, social, and environmental domains.Individual-level factors include demographic, economic, psychological, attitude and knowledge, and individual behavioral factors.Social-level factors encompass parental education, family member tobacco use, stressful life events, and social networks.Environmental factors include secondhand smoke exposure, community context, media channels, and access to tobacco.These factors were found to be significantly associated with tobacco use among youth in low-, lower-, and upper-middle-income countries.Consequently, it is imperative to implement targeted, tailored health interventions that aim to reduce tobacco use among individuals in diverse socioeconomic contexts.
• This review analyzed 20 cross-sectional studies focusing on factors associated with youth tobacco use in low-income, lower-middle-income, and upper-middle-income countries.

Figure 1 .
Figure 1.PRISMA flow chart.Note.PRIMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses

Figure 2 .
Figure 2. JBI Checklist for the Quality Assessment of Cross-sectional Studies.Q1.Were the criteria for inclusion in the sample clearly defined?Q2.Were the study subjects and the setting described in detail?Q3.Was the exposure measured in a valid and reliable way?Q4.Were objective, standard criteria used for the measurement of the condition?Q5.Were confounding factors identified?Q6.Were strategies to deal with confounding factors stated?Q7.Were the outcomes measured in a valid and reliable way?Q8.Was the applied statistical analysis appropriate?

Table 2 .
Summary of factors influencing tobacco use among youth based on the theory of triadic influence smoke exposure Secondhand smoke at home, public transport, and living in a smoker's environment b.Community context Rural area School location c.Media channels Smoking advertising Exposure to tobacco by radio d.Access of tobacco Easy availability Factors influencing the use of tobacco among youth

Table 1 .
48ntinuedFactors influencing the use of tobacco among youth was warranted if two or more weak ratings were across the eight evaluation components.48 • Three overarching domains emerged based on the theory of the triadic influence model, namely, Individual-, social-, and environmental-level factors.• Individual-level factors included demographic, economic, psychological, attitude, knowledge, and individual behavioral factors.• Social-level factors were parental education, family member tobacco use, stressful life events, and social networks.• Environmental-level factors encompassed secondhand smoke exposure, community context, media channels, and access to tobacco.